Electroluminescent display apparatus

Abstract

A display apparatus includes an organic electroluminescent element, a protective layer provided in contact with the organic electroluminescent element and configured to cover the organic electroluminescent element, and a condenser lens provided in contact with the protective layer and on a light output side of the organic electroluminescent element. The condenser lens includes a convex surface having a sloping angle θS that satisfies a predetermined mathematical condition.

1 . A display apparatus comprising:
 an organic electroluminescent element;   a protective layer provided in contact with the organic electroluminescent element and configured to cover the organic electroluminescent element; and   a condenser lens provided in contact with the protective layer and on a light output side of the organic electroluminescent element, the condenser lens having a convex surface opposite with respect to the organic electroluminescent element,   wherein, at a point on the convex surface where light emitted from the organic electroluminescent element is incident on the convex surface of the condenser lens, the condenser lens satisfies the following expression:
   sin [θ S −Arcsin {( n   1   /n   2 )×sin(θ S −θ)}]≧1 /n   2  
 
   
       where θ denotes an emission angle of the light emitted from the organic electroluminescent element and being incident on the convex surface of the condenser lens, θ S  denotes a sloping angle of the convex surface of the condenser lens at a point where the light emitted at the emission angle θ from the organic electroluminescent element is incident, n 1  denotes a refractive index of the condenser lens, and n 2  denotes a refractive index of a medium provided across the condenser lens from the organic electroluminescent element. 
     
     
         2 . The display apparatus according to  claim 1 , wherein the condenser lens includes a central portion and a peripheral portion that have different curvatures, and wherein the condenser lens satisfies the expression at a point in the peripheral portion thereof. 
     
     
         3 . The display apparatus according to  claim 1 , wherein the emission angle θ is 30 degrees or larger. 
     
     
         4 . The display apparatus according to  claim 1 , wherein the medium having the refractive index n 2  has a flat surface on a side thereof remote from the condenser lens.